Table of contents

1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

21. Aldehydes and Ketones: Nucleophilic Addition

Addition of Amine Derivatives

Organic Chemistry

21. Aldehydes and Ketones: Nucleophilic Addition

Addition of Amine Derivatives

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1:40 minutes

Problem 57b,c

Textbook Question

What aldehydes are formed when the following amino acids are treated with ninhydrin?
b. leucine
c. arginine

Verified step by step guidance

Understand the reaction: Ninhydrin reacts with amino acids to produce aldehydes, carbon dioxide, and ammonia. The aldehyde formed depends on the structure of the amino acid's side chain.

For leucine: Identify the structure of leucine. It has an isobutyl side chain (-CH2-CH(CH3)2). When treated with ninhydrin, the amino group is removed, and the side chain is converted into an aldehyde. The resulting aldehyde will have the structure of the side chain minus the terminal carbon.

For arginine: Identify the structure of arginine. It has a guanidino group (-C(NH2)2-NH) attached to a 3-carbon chain. When treated with ninhydrin, the guanidino group is removed, and the aldehyde formed will correspond to the 3-carbon chain.

Write the general reaction mechanism: Ninhydrin reacts with the amino group of the amino acid, forming a Schiff base intermediate. This intermediate undergoes decarboxylation and hydrolysis to yield the aldehyde.

Determine the specific aldehydes: For leucine, the aldehyde will be isobutyraldehyde (CH3-CH2-CHO). For arginine, the aldehyde will be 3-aminopropanal (H2N-CH2-CH2-CHO).

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Amino Acids

Amino acids are organic compounds that serve as the building blocks of proteins. Each amino acid has a central carbon atom bonded to an amino group, a carboxyl group, a hydrogen atom, and a variable side chain (R group) that determines its unique properties. Understanding the structure and properties of specific amino acids, such as leucine and arginine, is essential for predicting the products formed during chemical reactions.

Ninhydrin Reaction

The ninhydrin reaction is a chemical test used to detect amino acids and proteins. When amino acids react with ninhydrin, they undergo a dehydration reaction, resulting in the formation of a colored complex, typically a purple-blue hue. This reaction not only confirms the presence of amino acids but also leads to the formation of aldehydes, which are important for identifying the specific amino acids involved.

Aldehyde Formation

Aldehydes are organic compounds characterized by the presence of a carbonyl group (C=O) bonded to at least one hydrogen atom. In the context of the ninhydrin reaction, the amino acids leucine and arginine are converted into their corresponding aldehydes upon treatment with ninhydrin. Recognizing the specific aldehydes formed from these amino acids is crucial for understanding the outcomes of the reaction and the identification of the amino acids.

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